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gh-101881: Support (non-)blocking read/write functions on Windows pipes (GH-101882)

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* fileutils: handle non-blocking pipe IO on Windows

Handle erroring operations on non-blocking pipes by reading the _doserrno code.
Limit writes on non-blocking pipes that are too large.

* Support blocking functions on Windows

Use the GetNamedPipeHandleState and SetNamedPipeHandleState Win32 API functions to add support for os.get_blocking and os.set_blocking.
This commit is contained in:
Rayyan Ansari 2023-02-16 14:52:24 +00:00 • committed by GitHub
parent 36b139af63
commit 739c026f44
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GPG key ID: 4AEE18F83AFDEB23
8 changed files with 107 additions and 25 deletions
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93
Python/fileutils.c
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@ -1750,7 +1750,15 @@ _Py_read(int fd, void *buf, size_t count)
Py_BEGIN_ALLOW_THREADS
errno = 0;
#ifdef MS_WINDOWS
_doserrno = 0;
n = read(fd, buf, (int)count);
// read() on a non-blocking empty pipe fails with EINVAL, which is
// mapped from the Windows error code ERROR_NO_DATA.
if (n < 0 && errno == EINVAL) {
if (_doserrno == ERROR_NO_DATA) {
errno = EAGAIN;
}
}
#else
n = read(fd, buf, count);
#endif
@ -1804,6 +1812,7 @@ _Py_write_impl(int fd, const void *buf, size_t count, int gil_held)
}
}
}
#endif
if (count > _PY_WRITE_MAX) {
count = _PY_WRITE_MAX;
@ -1814,7 +1823,18 @@ _Py_write_impl(int fd, const void *buf, size_t count, int gil_held)
Py_BEGIN_ALLOW_THREADS
errno = 0;
#ifdef MS_WINDOWS
n = write(fd, buf, (int)count);
// write() on a non-blocking pipe fails with ENOSPC on Windows if
// the pipe lacks available space for the entire buffer.
int c = (int)count;
do {
_doserrno = 0;
n = write(fd, buf, c);
if (n >= 0 || errno != ENOSPC || _doserrno != 0) {
break;
}
errno = EAGAIN;
c /= 2;
} while (c > 0);
#else
n = write(fd, buf, count);
#endif
@ -1829,7 +1849,18 @@ _Py_write_impl(int fd, const void *buf, size_t count, int gil_held)
do {
errno = 0;
#ifdef MS_WINDOWS
n = write(fd, buf, (int)count);
// write() on a non-blocking pipe fails with ENOSPC on Windows if
// the pipe lacks available space for the entire buffer.
int c = (int)count;
do {
_doserrno = 0;
n = write(fd, buf, c);
if (n >= 0 || errno != ENOSPC || _doserrno != 0) {
break;
}
errno = EAGAIN;
c /= 2;
} while (c > 0);
#else
n = write(fd, buf, count);
#endif
@ -2450,6 +2481,64 @@ error:
return -1;
}
#else /* MS_WINDOWS */
int
_Py_get_blocking(int fd)
{
HANDLE handle;
DWORD mode;
BOOL success;
handle = _Py_get_osfhandle(fd);
if (handle == INVALID_HANDLE_VALUE) {
return -1;
}
Py_BEGIN_ALLOW_THREADS
success = GetNamedPipeHandleStateW(handle, &mode,
NULL, NULL, NULL, NULL, 0);
Py_END_ALLOW_THREADS
if (!success) {
PyErr_SetFromWindowsErr(0);
return -1;
}
return !(mode & PIPE_NOWAIT);
}
int
_Py_set_blocking(int fd, int blocking)
{
HANDLE handle;
DWORD mode;
BOOL success;
handle = _Py_get_osfhandle(fd);
if (handle == INVALID_HANDLE_VALUE) {
return -1;
}
Py_BEGIN_ALLOW_THREADS
success = GetNamedPipeHandleStateW(handle, &mode,
NULL, NULL, NULL, NULL, 0);
if (success) {
if (blocking) {
mode &= ~PIPE_NOWAIT;
}
else {
mode |= PIPE_NOWAIT;
}
success = SetNamedPipeHandleState(handle, &mode, NULL, NULL);
}
Py_END_ALLOW_THREADS
if (!success) {
PyErr_SetFromWindowsErr(0);
return -1;
}
return 0;
}
void*
_Py_get_osfhandle_noraise(int fd)
{